Portal themes not working

Hi

i hav downloaded flash player and developed a file.

which shows different images...i saved with extension of jpg.

wen i open this jpg file.its working properly...its changing images accrding to the time limit which i mentiond

i placed this .jpg file in master head....but its not working in portal.

the size of this file is 238kb only...y its not working in portal..if i opend it directly y its working.

kindly let me knw wer i m wrong n wat i hav to do

thanks and regards,

venkat